1. Field of the Invention
The present invention relates to a private branch exchange (PBX). More particularly, the present invention relates to a digital private branch exchange system for switching a short message service and a switching method.
2. Background of the Related Art
Generally, a private branch exchange is an exchange for switching between extension lines in a business site such as an office, a company, a factory, a hotel, etc. or for switching between an extension line and an office line. Methods for providing a short message service (SMS) to users of the extension lines connected to the private branch exchange by using the private branch exchange are being researched.
FIG. 1 is a construction view of a related art digital private branch exchange for switching the SMS. As shown in FIG. 1, a digital private branch exchange 10 for switching the SMS converts an SMS signal received through an office line such as a public switched telephone network (PSTN), an integrated services digital network (ISDN), etc. into a format corresponding to an extension line terminal 90 and then switches into the extension line terminal 90.
The extension line terminal 90 includes a single line terminal SLT for SMS 92 and a digital terminal 94. The private branch exchange 10 includes: an analog office line interface unit 20; an ISDN office line interface unit 30; a voice mail interface unit 40; a SLT extension line interface unit 60; a digital terminal extension line interface unit 70; and a main processor 50. The units 20, 30, 40, 50, 60, and 70 are connected to one another by an SMS data bus 80, and the main processor 50 controls SMS data exchange among the units.
The analog office line interface unit 20 interfaces with an analog office line such as the PSTN. The analog office line interface unit 20 includes an analog office line SMS unit 21 for detecting an SMS signal of a frequency shift keying (FSK) format transmitted through the analog office line and converting the detected SMS signal into SMS data. The SMS data can be data from the analyzed SMS signal.
The ISDN office line interface unit 30 interfaces with an ISDN office line. The ISDN office line interface unit 30 includes an ISDN office line SMS unit 31 for detecting an SMS signal of a pulse code modulation (PCM) format transmitted through the ISDN office line and converting the detected SMS signal into SMS data.
The voice mail interface unit 40 provides a voice mail service function. The voice mail interface unit 40 includes a digital signal processor (DSP) 41 for compressing voice and reproducing the compressed voice, and a memory 42 for storing the voice compressed by the DSP 41.
The main processor 50 controls the entire private branch exchange 10. The main processor 50 certifies an extension line terminal that will receive the SMS and transmit the SMS to the corresponding extension line terminal.
The SLT extension line interface unit 60 connects the SLT 92 and the private branch exchange 10. The SLT extension line interface unit 60 includes a SLT extension line SMS unit 61 for converting SMS data transmitted from the main processor 50 into an SMS signal of an FSK format. The digital terminal extension line interface unit 70 connects the private branch exchange with the digital terminal 94, and transmits SMS data transmitted from the main processor 50 to the corresponding digital terminal 94.
Operations for switching SMS in the digital private branch exchange 10 will now be described. FIG. 2 shows a method for switching SMS in the digital private branch exchange. As shown in FIG. 2, if a speech path is connected between the private branch exchange 10 and the office line board (the analog office line interface unit 20) or the ISDN office line interface unit 30 before the SMS signal is received, the private branch exchange 10 certifies whether a corresponding SMS unit is connected to a corresponding office line board or not (S12).
If the corresponding SMS unit is not connected to the corresponding office line board, the private branch exchange 10 finishes a procedure for receiving the SMS. However, if the corresponding SMS unit is connected to the corresponding office line board, the private branch exchange 10 finishes signaling for receiving the SMS by using the corresponding SMS unit and then receives the SMS signal (S14). When the corresponding office line board is the analog office line interface unit 20, the analog office line SMS unit 21 receives an SMS signal of an FSK format, and when the corresponding office line board is the ISDN office line interface unit 30, the ISDN office line SMS unit 31 receives an SMS signal of pulse code modulation format.
The corresponding SMS unit which has received the SMS signal converts the SMS signal into SMS data and then transmits to the main processor 50 through the SMS data bus 80. That is, the analog office line SMS unit 21 converts the SMS of an FSK format into the SMS data, and the ISDN office line SMS unit 31 converts the SMS signal of a PCM format into the SMS data (S16).
The main processor 50 certifies that a receiving terminal of the SMS is an SLT or a digital terminal on the basis of the received SMS data (S18). If the receiving terminal of the SMS (an extension line terminal which will receive the SMS data) is the SLT 92, the main processor 50 certifies whether the SLT extension line interface unit 60 connected to the SLT 92 is provided with the SLT extension line SMS unit 61 or not (S20). If the SLT extension line SMS unit is connected to the SLT extension line interface unit 60, the main processor 50 transmits the SMS data to the SLT extension line interface unit 60 (S22).
The SLT extension line SMS unit 61 of the SLT extension line interface unit 60 performs signaling with the SLT 92 (S24), and converts the SMS data into an SMS signal of an FSK format then transmits the converted SMS signal of an FSK format to the SLT 92 (S26). Then, the SLT 92 displays the received SMS signal on a display unit.
However, if the receiving terminal of the SMS (the extension line terminal which will receive the SMS data) is the digital terminal 94 (S18), the main processor 50 transmits the SMS data to the digital terminal extension line interface unit 70 (S28). The digital terminal extension line interface unit 70 transmits the SMS data to the corresponding digital terminal 94 (S30). The digital terminal 94 displays the transmitted SMS data on the display unit.
As described above, the related art SMS switching PBX and methods have various disadvantages. For example, in the related art SMS switching private branch exchange, each port of the analog office line interface unit, the ISDN office line interface unit, and the SLT extension line interface unit has to be provided with an SMS unit for exclusive use. Thus, the SMS can not be provided through an office line or the SLT extension line to which an SMS unit is not connected for exclusive use.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.